There is no way to show schema permissions in psql.
The alternatives are:

1) A new \dpn command
2) Extend \dp to also show rights for schemas, but then we need
an extra column to describe what kind of object it is, and it
would mess up the pattern stuff.
3) Do nothing and let people who want to see schema permissions
query the system table (select * from pg_namespace).
4) Since \dn only shows the name and the owner we can simply
add a permission column.
5) Some better way that is unknow to me
I've attached a patch for number 4) which I think is the best. Well, 5) is
better, but also harder to implement.
--
/Dennis Björklund